Digestion And Enzymes. Flashcards
What is an enzyme?
Proteins that act as biological catalysts, meaning they speed up reactions without being used up.
They are specific to one type of molecule.
What is the name of the molecule that enzymes work on?
The substrate.
What are the molecules formed by an enzyme reaction called?
Products.
What is the connection point between an enzyme and substrate called?
The active site.
The active site and the substrate are complementary in shape, so they only work on one type of molecule.
This is the “Lock and key model”
What is formed when an enzyme and substrate collide?
Enzyme-substrate complex
It is in this complex where the reaction takes place.
List 4 different enzymes, their substrate and the reaction products.
Carbohydrase Carbohydrate Simple sugar, glucose
Amylase Starch Simple sugar, glucose
Protease Protein Amino acid
Lipase Fat (Lipid) Glycerol and fatty acids
What molecules reduce the rate of reaction and how do they do this?
Inhibitors.
They fit loosely or partially in the active site of the enzyme, which means substrate molecules cannot enter, which leads to a reduced (inhibited) rate of reaction.
How does temperature affect enzyme activity?
At low temperatures, the enzyme and substrate molecules have reduced kinetic energy and move slowly, resulting in few collisions between them.
At higher temperatures the enzyme and substrate molecules have increased kinetic energy, increasing the number of collisions and the rate of activity.
This works up to a certain point called the optimum. Once temperatures exceed the optimum, enzyme activity decreases sharply. This is due to an irreversible change in the shape of the enzymes active site, known as denaturation.
What is a thermostable enzyme?
They work at a wide range if temperatures.
How does pH affect enzyme activity?
Most enzymes only work at a specific pH range. Deviating from the optimum pH will cause the active site to become denatured.
How does Enzyme concentration effect the rate of reaction?
The higher the enzyme concentration the more likely a substrate and enzyme will collide, increasing the rate of reaction.
This occurs up to a certain point, after which enzyme activity plateaus as there aren’t enough substrate molecules to react with the extra enzymes.
What is the definition of digestion?
The breakdown of large, complex, insoluble molecules into small, simple, soluble ones.
What is the the function of the ileum?
Although the final stages of digestion take place in the small intestine, the main function of the ilium is the absorption of digested food products.
What are some adaptations for the ileum?
Large surface area due to being long and folded
Thin so digested food products doesn’t have to travel far to reach the blood.
Permeable so digested food can pass through easily
Good blood supply to maintain the concentration gradient for diffusion between the ileum and bloodstream.
Villi finger like projections that further increase surface area.
What are some adaptations of the villus?
Good blood supply. A villus has a large network of capillaries for transporting food products.
Lacteal. A tube that absorbs the products of fat digestion before returning them to the blood.
Single layer of surface epithelium cells, i.e. walls only one cell thick, reducing the diffusion distance.
Permeable, so digested food products can pass through easily.
What are carbohydrates?
Carbohydrates provide energy.
There are two types, simple and complex
Simple carbohydrates are sugars, like glucose and lactose. They are a fast acting source of energy.
Complex carbohydrates are a slow release of energy, like cellulose, starch and glycogen. They are long chains of sugars.
Learn the diagrams of these molecules.
What are lipids?
Fats.
Fats are a store of energy, providing double the energy that carbohydrates and proteins do.
They are made up of fatty acids and glycerol.
Learn the diagram for these molecules.
What are proteins?
Protein is used for the growth and repair of cells.
It can be used as a source of energy if carbohydrate and fat reserves are low.
They are made if long chains of amino acids.
After digestion amino acids are absorbed into the bloodstream and brought to cells that reassemble them into proteins needed by the body.
Learn the diagrams for these molecules.
How do you test for sugar?
Benedict’s reagent.
Add the reagent to the food and boil in a water bath.
The reagent will start blue, and a positive result will turn brick red.
How do you test for starch?
Iodine.
Add iodine reagent to the food.
The reagent will start yellow brown, but a positive result will turn it blue-black
How do you test for protein/amino acid?
Biuret.
Add biuret reagent to food.
It will start blue, and a positive result will turn it lilac/purple
How do you test for fat?
Ethanol.
Add ethanol to food to dissolve the fat then add water.
It will start colourless, but a positive result will turn it cloudy white.
What three elements are found in all biological molecules?
Carbon
Hydrogen
Oxygen
What are some modern uses for enzymes?
Washing powders- to remove stains.
